Nested subroutine calls in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call a subroutine named 'func1'.

ARM Architecture

[1] func1

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ABL

BB

CBX

DMOV

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'B' instead of 'BL' which does not save the return address.

Forgetting to specify the subroutine name after the instruction.

The BL instruction is used to branch to a subroutine and link the return address.

2fill in blank

medium

Complete the code to call 'func2' from within 'func1'.

ARM Architecture

func1:
    BL [1]
    BX LR

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Afunc2

Bmain

Cfunc3

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the wrong subroutine name.

Using 'BX LR' instead of 'BL' to call the subroutine.

Inside 'func1', the subroutine 'func2' is called using the BL instruction followed by 'func2'.

3fill in blank

hard

Fix the error in the nested call where 'func3' is called incorrectly.

ARM Architecture

func2:
    BL [1]
    BX LR

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Afunc2

Bmain

Cfunc1

Dfunc3

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'func1' or 'func2' instead of 'func3'.

Using 'BX LR' instead of 'BL' for the call.

The nested call inside 'func2' should call 'func3' using the BL instruction followed by 'func3'.

4fill in blank

hard

Fill both blanks to correctly call 'func2' and then return from 'func1'.

ARM Architecture

func1:
    [1] [2]
    BX LR

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ABL

Bfunc2

CB

Dfunc3

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'B' instead of 'BL' for the call.

Calling the wrong subroutine name.

The instruction BL func2 calls 'func2' and saves the return address. Then BX LR returns from 'func1'.

5fill in blank

hard

Fill all three blanks to call 'func3' from 'func2' and then return properly.

ARM Architecture

func2:
    [1] [2]
    [3] LR

Drag options to blanks, or click blank then click option'

ABL

Bfunc3

CBX

Dfunc1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'B' instead of 'BL' for the call.

Calling the wrong subroutine name.

Using incorrect return instruction.

The instruction BL func3 calls 'func3' and saves the return address. Then BX LR returns from 'func2'.